With the rapid expansion of digital data processing in recent years, much of the research has attempted to discover new methods and materials for use in such data processing equipment. One of the most important considerations in these research efforts is an increase in the speed at which the computations may be made.
It is believed that if logic operations can be performed in a completely optical manner that a significant break-through in processing speed may be achieved relative to digital data processing in conventional electronic and electro-optical systems.
The development of the laser has led many investigators to explore different materials for the existence of lasing properties. One class of materials in which considerable interest has been shown is known as laser dyes. The dye lasers utilize organic dyes as the laser medium. A large number of such dyes have been discovered and described in the literature. A dye, generally known as Rhodamine 6G, has been found to be particularly useful for a variety of laser applications. Dye lasers are described in detail in U.S. Pat. No. 3,679,995, the subject matter of which is incorporated herein by reference.
A unique feature of the dyes used in dye laser configurations is that a collimated laser output beam can be generated whose direction of polarization can be predominantly determined by the polarization direction of the pumping energy employed to excite the dye laser if that pumping light is injected axially into the dye laser cavity. This characteristic has been described at length in the art, see, for example, Section 3.8 on page 62 of a book entitled Handbook of Fluorescence Spectra of Aromatic Molecules, written by I. B. Berlman and published by the Academic Press in 1971. Another publication describing the dependence of the direction of polarization of the luminescence eminating from a fluorescing material upon the direction of polarization of exciting light appears in Section 9, page 163 of a book by P. P. Feofilov entitled The Physical Basis of Polarized Emission, published by Consultants Bureau, 1961.
Simply stated, the dye molecules are non-spherical and the electric dipole moment for optical transitions is anisotropic. A given molecule in the laser medium is randomly oriented, giving those molecules whose dipole moments are aligned with the direction of polarization of the exciting energy the highest probability of excitation. If the orientational rotation is sufficiently slow relative to the lifetime of the excited state, the emitted light has a preferred direction of polarization. In a laser which is sensitive to small differences in gain, the effect is a complete polarization of the laser emission. If the losses are isotropic, the direction of polarization of the output is the same as that of the exciting energy.